Impact craters are divided into two groups based on
morphology: simple craters and complex craters. Simple
craters are relatively small with depth-to-diameter ratios of
about 1:5 to 1:7 and a smooth bowl shape. In larger craters, however,
gravity causes the initially steep crater walls to collapse downward
and inward, forming a complex structure with a central peak or peak ring
and a shallower depth compared to diameter (1:10 to 1:20).